The present invention relates to a joint mechanism, more particularly, to a joint mechanism for an umbrella.
An umbrella generally includes stretchers that are connected to a runner which is slidably mounted on a metal rod at one end, and the other end is connected to a rib member via a joint. When the runner moves to its highest position, the stretchers are fully extended and the gore expands.
In the conventional art, the joint is made from metal and the rib members and the stretchers are made from fiber reinforced plastic (FRP) material. In assembly, the joint is firstly fixed to a suitable position, normally in the middle position, then the tip of the stretcher is riveted thereto. As shown in FIG. 4, two holes 222 in line are disposed at the lug of the joint 22 fixed at rib member 11. A cooperating hole is provided at the joint 21 of said stretcher 12. When the holes of joints 21 and 22 are aligned, a rivet 13 is inserted therein and then the other tip of said rivet is expanded to retain said rivet 13 from escaping. From the above description, it will be evident that the assembly is quite complicated and time-consuming as well as costly. Also, the machining of the rivet can only be smoothly done by a technician. Because there are at least eight rivets in a single umbrella, the defect rate cannot be lowered below a certain level. The increased cost and assembling time have a negative effect on the competitive ability of the manufacturer.